US8478558B2 - Method for processing a temperature sensor signal - Google Patents
Method for processing a temperature sensor signal Download PDFInfo
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- US8478558B2 US8478558B2 US12/338,709 US33870908A US8478558B2 US 8478558 B2 US8478558 B2 US 8478558B2 US 33870908 A US33870908 A US 33870908A US 8478558 B2 US8478558 B2 US 8478558B2
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- 238000000034 method Methods 0.000 title claims abstract description 27
- 238000012545 processing Methods 0.000 title claims abstract description 10
- 230000001419 dependent effect Effects 0.000 claims description 6
- 238000004891 communication Methods 0.000 description 6
- 238000006243 chemical reaction Methods 0.000 description 4
- 238000012546 transfer Methods 0.000 description 4
- 238000002485 combustion reaction Methods 0.000 description 2
- 239000002826 coolant Substances 0.000 description 2
- 210000003127 knee Anatomy 0.000 description 2
- 230000007704 transition Effects 0.000 description 2
- 230000003466 anti-cipated effect Effects 0.000 description 1
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 1
- 238000001816 cooling Methods 0.000 description 1
- 238000013461 design Methods 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 238000009429 electrical wiring Methods 0.000 description 1
- 230000006870 function Effects 0.000 description 1
- 229910052760 oxygen Inorganic materials 0.000 description 1
- 239000001301 oxygen Substances 0.000 description 1
- 238000011160 research Methods 0.000 description 1
- 238000005070 sampling Methods 0.000 description 1
- 239000007787 solid Substances 0.000 description 1
- 239000007858 starting material Substances 0.000 description 1
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Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01K—MEASURING TEMPERATURE; MEASURING QUANTITY OF HEAT; THERMALLY-SENSITIVE ELEMENTS NOT OTHERWISE PROVIDED FOR
- G01K7/00—Measuring temperature based on the use of electric or magnetic elements directly sensitive to heat ; Power supply therefor, e.g. using thermoelectric elements
- G01K7/42—Circuits effecting compensation of thermal inertia; Circuits for predicting the stationary value of a temperature
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01K—MEASURING TEMPERATURE; MEASURING QUANTITY OF HEAT; THERMALLY-SENSITIVE ELEMENTS NOT OTHERWISE PROVIDED FOR
- G01K7/00—Measuring temperature based on the use of electric or magnetic elements directly sensitive to heat ; Power supply therefor, e.g. using thermoelectric elements
- G01K7/16—Measuring temperature based on the use of electric or magnetic elements directly sensitive to heat ; Power supply therefor, e.g. using thermoelectric elements using resistive elements
- G01K7/22—Measuring temperature based on the use of electric or magnetic elements directly sensitive to heat ; Power supply therefor, e.g. using thermoelectric elements using resistive elements the element being a non-linear resistance, e.g. thermistor
- G01K7/24—Measuring temperature based on the use of electric or magnetic elements directly sensitive to heat ; Power supply therefor, e.g. using thermoelectric elements using resistive elements the element being a non-linear resistance, e.g. thermistor in a specially-adapted circuit, e.g. bridge circuit
- G01K7/25—Measuring temperature based on the use of electric or magnetic elements directly sensitive to heat ; Power supply therefor, e.g. using thermoelectric elements using resistive elements the element being a non-linear resistance, e.g. thermistor in a specially-adapted circuit, e.g. bridge circuit for modifying the output characteristic, e.g. linearising
Definitions
- the present invention relates to a temperature sensors; and in particular to processing a temperature sensor output signal that varies non-linearly with temperature.
- microcomputer responds to different parameters of the engine which are sensed.
- One of those parameters is engine temperature that is derived from a sensor sensing the temperature of the coolant for the engine.
- a common temperature sensor produces an output signal that is converted to a pulse width modulated signal indicating the sensed temperature.
- a characteristic of the PWM output signal such as the duration of either the high or low signal level portion, varies to denote the temperature that was sensed. In many sensors of this type, the signal varies in a non-linear manner with temperature. On a graph of the PWM signal values versus temperature, the resultant plot would be a series of linear sections having different slopes connected together.
- the control circuit has to employ relatively complex signal processing to accurately convert a value derived from the PWM sensor signal to the corresponding temperature.
- a common prior technique involved storing, in the engine control computer, sets of data defining the slopes of each linear section of the PWM sensor signal to temperature relationship for different starting temperatures. The accuracy of the signal conversion depended upon the number of different slope segments employed to represent each starting temperature based signal relationship.
- the initial temperature was sensed and used to select the set of data for the associated PWM sensor signal to temperature relationship.
- the slope for the corresponding section of the selected set of data was determined and used to convert the PWM signal value into a temperature value. That technique required several data access and calculation steps and therefore required a substantial amount of computer processing.
- a sensor on an apparatus produces an output the signal with a characteristic that varies non-linearly and non-exponentially with changes in a parameter being sensed.
- a method for processing that sensor signal defines an exponential equation that specifies a relationship between variation of the signal characteristic and the parameter being sensed. Upon receiving the signal from the sensor, the characteristic of the signal is measured to produce a sensor value. Then the sensor value is used to solve the exponential equation thereby producing a value for the parameter that is sensed by the sensor.
- a temperature sensor on an engine and the related circuitry produce a pulse width modulated signal that has portion, the duration of which varies non-linearly and non-exponentially with engine temperature changes.
- the duration of that portion of the signal is measured to produce a sensor value.
- the relationship between variation of the signal characteristic and the parameter being sensed is dependent upon an initial temperature when the engine starts operating and a steady state operating temperature of the engine.
- the exponential equation contains one term corresponding to the initial temperature and another term corresponding to the steady state operating temperature.
- FIG. 1 depicts components of a typical engine-generator set that incorporates the present invention
- FIG. 2 is a schematic block diagram of the engine control circuit in FIG. 1 that processes an output signal from a temperature sensor on the engine;
- FIG. 3 is a graph of the relationship between the temperature and the output signal from a temperature sensor.
- an engine-generator set 10 comprises an engine 12 and coupled directly by a shaft 14 to a generator 16 .
- This engine-generator set 10 is commonly used to provide back-up electrical power to a building in the event that power from a utility company is interrupted. That interruption is automatically sensed by an automatic transfer switch (not shown) which is connected to the utility lines and the output 15 of the generator.
- an automatic transfer switch detects that the utility power is unavailable, a signal is sent commanding the engine-generator set 10 to start. Shortly thereafter, the automatic transfer switch disconnects the building's electrical wiring from the utility lines and connects that wiring to the output 15 of the engine-generator set.
- the start command from the automatic transfer switch is received by the engine-generator set 10 at an operator control panel 25 that is connected via a communication bus 24 to a generator control circuit 18 and an engine control circuit 20 .
- the communication bus 24 may conform to the Computer Area Network (CAN) J-1939 standard promulgated by SAE International, formerly known as the Society of Automotive Engineers, Inc., however a communication bus using another protocol may be used.
- the generator control circuit 18 and the engine control circuit 20 respectively control the operation of the generator 16 and the internal combustion engine 12 .
- the engine control circuit 20 is built around a microcomputer 26 which includes a memory that stores a control program and data for operating of the engine.
- the microcomputer 26 has internal interface circuits for receiving signals from components on the engine and for producing output signals to control other devices.
- the microcomputer 26 receives signals from several sensors on the engine 12 , such as an engine temperature sensor 30 in the coolant system, an oil pressure sensor 31 , and an oxygen sensor 32 . Additional sensors and other devices may provide input signals to the microcomputer 26 .
- the microcomputer 26 produces output signals to control the engine starter 22 and the ignition system 23 .
- the command to start the engine-generator set 10 is received from the operator control panel 25 via the CAN communication bus 24 at a CAN bus interface circuit 28 connected to the microcomputer 26 .
- the engine control circuit 20 also exchanges other messages with the operator control panel 25 and the generator control circuit 18 via the CAN communication bus 24 .
- the present invention relates to the manner in which the microcomputer 26 processes the signal produced by the engine temperature sensor 30 .
- the engine temperature sensor 30 comprises a sensing device 34 and a signal converter 36 .
- the sensing device 34 which may be a Series 5024-0805 device from Airpax Corporation, Frederick, Md., USA., produces an analog signal that is transformed by the signal converter 36 into a pulse width modulated output signal having a characteristic that is varied to indicate the sensed temperature. For example the duty cycle of that signal may vary, or the duration of a high signal level portion of the PWM cycle can remain constant while the duration of a low signal level portion varies in relation to the sensed temperature.
- the PWM output signal from the signal converter 36 is applied to an input of the microcomputer 26 .
- the control program executed by the microcomputer 26 desires to read the temperature from sensor 30 , the control program begins sampling the sensor signal at the corresponding microcomputer input and measures the signal characteristic that indicates the sensed temperature. For example, if the duty cycle varies with temperature, the microcomputer measures the duration of the high signal level portion of the PWM sensor output signal. Specifically upon finding a low to high signal level transition, the microcomputer begins a timer that is periodically incremented, every millisecond for example. When the microcomputer then detects a high to low signal level transition, the timer is stopped.
- the resultant timer value also referred to herein as the PWM signal value, corresponds in a known manner to the engine temperature that was sensed.
- the output signal from the temperature sensor 30 is non-linear and non-exponential, an exemplary output signal is depicted by the solid curve in FIG. 3 which is formed by several segments having different slopes that are joined at knees, such as knee 40 .
- the exact contour of that curve, i.e. the slopes of the different segments, is dependent upon the starting temperature of the engine.
- the engine temperature ultimately increases to a steady state temperature, which is the temperature normally encountered when the cooling system for the engine is functioning properly.
- the steady state temperature is known from either the engine design specifications or empirical data.
- the present method conceptually fits an exponential curve, denoted by the dashed line in FIG. 3 , to the plot of the PWM signal values produced by the engine temperature sensor 30 . That curve defines the following exponential equation:
- T T ⁇ + T i - T ⁇ e kt
- T ⁇ the steady state temperature
- T i the initial temperature when the engine started
- k an exponential constant
- t the PWM signal value that indicates the present temperature.
- the value of the exponential constant k depends upon the sensor signal to temperature relationship for a particular model of sensor and can be determined empirically. For example, four is the value of the exponential constant is used with the Airpax Series 5024-0805 temperature sensor mentioned above.
- the steady state temperature used in this equation is a fixed value for a particular engine.
- the initial temperature is determined by the microcomputer 26 reading the signal from the engine temperature sensor 30 at the time the engine is started. That initial temperature usually is the ambient temperature of the environment in which the engine-generator set is located. At this relatively low temperature in the operating range of the sensor, the relationship between the PWM signal value and temperature is relatively constant, as compared to the relationship for higher temperatures. Therefore, microcomputer is able to obtain the initial temperature with a direct conversion that does not require solving the exponential equation given above.
- the initial temperature is stored in the microcomputer memory.
- the microcomputer 26 Each time thereafter that the microcomputer 26 desires to obtain the present engine temperature, it reads the signal from the engine temperature sensor 30 . The microcomputer measures the characteristic of that signal as described above. The resultant PWM signal value is then used as the variable t in the exponential equation to derive the present temperature of the engine. The resultant engine temperature valve is sent via the CAN communication bus 24 to the operator control panel 25 , which displays that value on an engine temperature indicator.
- Fitting an exponential function to the actual output data from the engine temperature sensor 30 greatly simplifies the conversion of the sensor's PWM signal value to the corresponding temperature. Because, only the initial engine temperature needs to known besides the present output of the temperature sensor the conversion is very straight forward.
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- Physics & Mathematics (AREA)
- General Physics & Mathematics (AREA)
- Nonlinear Science (AREA)
- Combined Controls Of Internal Combustion Engines (AREA)
Abstract
Description
where T is the present engine temperature, T∞ is the steady state temperature, Ti is the initial temperature when the engine started, k is an exponential constant, and t is the PWM signal value that indicates the present temperature. The value of the exponential constant k depends upon the sensor signal to temperature relationship for a particular model of sensor and can be determined empirically. For example, four is the value of the exponential constant is used with the Airpax Series 5024-0805 temperature sensor mentioned above. The steady state temperature used in this equation is a fixed value for a particular engine.
Claims (13)
Priority Applications (2)
Application Number | Priority Date | Filing Date | Title |
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US12/338,709 US8478558B2 (en) | 2008-12-18 | 2008-12-18 | Method for processing a temperature sensor signal |
PCT/US2009/006368 WO2010080093A1 (en) | 2008-12-18 | 2009-12-03 | Method for processing a temperature sensor signal |
Applications Claiming Priority (1)
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US12/338,709 US8478558B2 (en) | 2008-12-18 | 2008-12-18 | Method for processing a temperature sensor signal |
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US20100161270A1 US20100161270A1 (en) | 2010-06-24 |
US8478558B2 true US8478558B2 (en) | 2013-07-02 |
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WO (1) | WO2010080093A1 (en) |
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US8872361B2 (en) | 2012-01-25 | 2014-10-28 | Briggs & Stratton Corporation | Standby generators including compressed fiberglass components |
US11705779B2 (en) | 2020-06-03 | 2023-07-18 | Briggs & Stratton, Llc | Inverter generator |
US11591977B2 (en) | 2020-06-03 | 2023-02-28 | Briggs & Stratton, Llc | Inverter generator |
Citations (14)
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---|---|---|---|---|
US3973147A (en) * | 1975-10-28 | 1976-08-03 | General Motors Corporation | Temperature measuring circuit |
US4464067A (en) * | 1982-01-22 | 1984-08-07 | Citizen Watch Company Limited | Thermistor frequency controlled electronic thermometer |
US4471354A (en) * | 1981-11-23 | 1984-09-11 | Marathon Medical Equipment Corporation | Apparatus and method for remotely measuring temperature |
US4602871A (en) * | 1984-10-23 | 1986-07-29 | Citizen Watch Co., Ltd. | Thermistor thermometer |
US5832721A (en) * | 1996-10-15 | 1998-11-10 | Ford Global Technologies, Inc. | Method and system for estimating a midbed temperature of a catalytic converter in an exhaust system having a variable length exhaust pipe |
US5857777A (en) | 1996-09-25 | 1999-01-12 | Claud S. Gordon Company | Smart temperature sensing device |
US5948368A (en) | 1996-01-09 | 1999-09-07 | Fuji Photo Film Co., Ltd. | Method of determining calibration curve and analysis method and apparatus using the same |
US6363332B1 (en) * | 1998-12-22 | 2002-03-26 | Caterpillar Inc. | Method and apparatus for predicting a fault condition using non-linear curve fitting techniques |
US20020114375A1 (en) * | 1997-06-24 | 2002-08-22 | Exergen Corporation | Ambient and perfusion normalized temperature detector |
US6827487B2 (en) | 2001-02-16 | 2004-12-07 | Per Lennart Baumbach | Temperature measuring device |
US20070171055A1 (en) | 2004-06-10 | 2007-07-26 | Abb Oy | Isolated measurement circuit for sensor resistance |
US20080043809A1 (en) | 2006-08-18 | 2008-02-21 | Herbert Curtis B | Thermometer |
US20080099570A1 (en) | 2006-10-04 | 2008-05-01 | Steve Krebs | System and method for estimating temperature drift and drive curves |
US7413343B2 (en) | 2005-09-16 | 2008-08-19 | Kyocera Wireless Corp. | Apparatus for determining a temperature sensing element |
-
2008
- 2008-12-18 US US12/338,709 patent/US8478558B2/en active Active
-
2009
- 2009-12-03 WO PCT/US2009/006368 patent/WO2010080093A1/en active Application Filing
Patent Citations (14)
Publication number | Priority date | Publication date | Assignee | Title |
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US3973147A (en) * | 1975-10-28 | 1976-08-03 | General Motors Corporation | Temperature measuring circuit |
US4471354A (en) * | 1981-11-23 | 1984-09-11 | Marathon Medical Equipment Corporation | Apparatus and method for remotely measuring temperature |
US4464067A (en) * | 1982-01-22 | 1984-08-07 | Citizen Watch Company Limited | Thermistor frequency controlled electronic thermometer |
US4602871A (en) * | 1984-10-23 | 1986-07-29 | Citizen Watch Co., Ltd. | Thermistor thermometer |
US5948368A (en) | 1996-01-09 | 1999-09-07 | Fuji Photo Film Co., Ltd. | Method of determining calibration curve and analysis method and apparatus using the same |
US5857777A (en) | 1996-09-25 | 1999-01-12 | Claud S. Gordon Company | Smart temperature sensing device |
US5832721A (en) * | 1996-10-15 | 1998-11-10 | Ford Global Technologies, Inc. | Method and system for estimating a midbed temperature of a catalytic converter in an exhaust system having a variable length exhaust pipe |
US20020114375A1 (en) * | 1997-06-24 | 2002-08-22 | Exergen Corporation | Ambient and perfusion normalized temperature detector |
US6363332B1 (en) * | 1998-12-22 | 2002-03-26 | Caterpillar Inc. | Method and apparatus for predicting a fault condition using non-linear curve fitting techniques |
US6827487B2 (en) | 2001-02-16 | 2004-12-07 | Per Lennart Baumbach | Temperature measuring device |
US20070171055A1 (en) | 2004-06-10 | 2007-07-26 | Abb Oy | Isolated measurement circuit for sensor resistance |
US7413343B2 (en) | 2005-09-16 | 2008-08-19 | Kyocera Wireless Corp. | Apparatus for determining a temperature sensing element |
US20080043809A1 (en) | 2006-08-18 | 2008-02-21 | Herbert Curtis B | Thermometer |
US20080099570A1 (en) | 2006-10-04 | 2008-05-01 | Steve Krebs | System and method for estimating temperature drift and drive curves |
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Title |
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MAXIM, Four-Channel Thermistor Temperature-to-Pulse-Width Converter. MAX6691. Maxim Integrated Products, CA. 2007. * |
Paul Horowitz, Winfield Hill,: "The Art of Electronics", 1980, pp. 579-580, Cambridge University Press, Cambridge, ISBN: 0521231515. |
Qingshan Shan, et al., "Wireless Monitoring System for Vehicle Refrigerator", 2005 IEEE International Conference on Information Acquisition Jun. 27-Jul. 3, 2005, Hong Kong and Macau, China, pp. 417-420, IEEE, Piscataway, NJ. |
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WO2010080093A1 (en) | 2010-07-15 |
US20100161270A1 (en) | 2010-06-24 |
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